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| Artist’s impression of LISA Pathfinder, which will look for gravitational waves in space. Credit: ESA–D. DUCROS |
The fabric of spacetime is continually being stretched and squeezed due to the motion of all the bodies of the universe. These fluctuations are called gravitational waves and an upgraded, ground-based set of stations called the Laser Interferometer Gravitational-Wave Observatory (LIGO) is currently trying to probe them with unprecedented sensitivity.
However, astronomers would love to measure gravitational waves in space with even better resolution, but that requires two satellites separated by millions of miles. Even over these extreme distances, the gravitational wave’s influence on the warping of spacetime will be minuscule, requiring precise measurements.
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Luckily for science, the European Space Agency will launch a large-scale gravitational wave observatory in 2034, although the design of it isn’t yet finalized. Previous concepts called Laser Interferometer Space Antenna (LISA) and New Gravitational wave Observatory (NGO) have been studied in detail but were not selected.
That’s where LISA Pathfinder comes in. It won’t actually hunt for gravitational waves, but will work out the kinks for the much larger mission in a couple of decades. And project scientist Paul McNamara plans to be there for both launches.
“What I really wanted to do (with my career) is gravitational wave astrophysics ,” McNamara told Discovery News, adding he started working on LISA at age 21, in 1994. That will put him close to retirement age when the 2034 mission gets off the ground.
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LISA Pathfinder will need to be an extraordinarily quiet and stable spacecraft. It will carry two 2 kilogram (4.4-pound) precious payloads — test masses of a gold-platinum alloy — that it needs to shield from the stresses of launch, the pressure of solar radiation, and the extreme environment of space. Also, no magnetic materials can be used during construction, among other requirements.
It also will need to travel a stable orbit so that the effect of the earth and moon doesn’t perturb the masses too much. So the spacecraft will orbit a region called the Sun Earth Lagrange point, L1 — 1.5 million kilometers or 932,000 miles closer to the sun than the Earth’s orbit. This requires once-a-week orbit adjustments. The 2034 successor mission, fortunately, will orbit the sun and not require any adjustments in its five-year mission.
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The gold platinum masses are separated by 38 centimeters (15 inches) and that distance will be measured by a laser interferometer. Under ideal conditions, the investigators hope to see no motion. They’ll run this “clock” for 90 days, only taking a break for orbital adjustments. If the money is there, there’s enough to fuel to last a year. The extended mission (if approved) will test more intrusive spacecraft maneuvers to see what happens with the masses, McNamara said.
LISA Pathfinder is on its way to its launch pad in French Guiana in September for an expected launch date in the last week of November.
This article was provided by Discovery News .
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